Bus bars composed of pure-copper sheets having excellent electrical conductivity and strength, such as oxygen-free copper, tough-pitch copper, or oxygen-free phosphorus-containing copper, are used as conductive members for the wiring of power control units (PCUs) or the like in transportation machines, for example, the Shinkansen, linear motor cars, hybrid automobiles, and electrical vehicles. In addition, if strength greater than that of a pure-copper sheet is needed, then a bus bar or the like is used in which a copper-alloy sheet having high electrical conductivity is subjected to electrolytic nickel plating.
From the viewpoint of improving the energy efficiency of transportation machines, there has been a strong demand in recent years to reduce the weight of the component parts. However, among the metals used as electrically conductive members, there is a limit to the extent to which the weight of a bus bar that uses copper can be reduced, because copper has a relatively large specific gravity. In addition, there is a problem in that the material cost of copper is high.
As a counter measure for such problems, bus bars made of aluminum alloys, which have a lower cost and smaller specific gravity than copper, are being studied. JIS A 1060 material (Patent Document 1), which excels in electrical conductivity, JIS A 6101 material (Patent Document 2), which excels in strength, and the like have been proposed as examples of aluminum materials for bus bars.